Zonal sedimentation analysis on sucrose gradients allows estimation of the molecular size of an individual protein or a protein complex by centrifugation at a constant speed under nondenaturing conditions. This method is particularly suitable for globular proteins like the influenza A virus (IAV) protein hemagglutinin (HA). Here, I describe step by step a protocol used to evaluate the oligomeri...

BACKGROUND Numerous Asian cases of avian influenza virus infection, especially the highly pathogenic strain H5N1, in humans have raised the concern that another influenza pandemic is close. However, there are no effective therapeutic drugs or preventative vaccines available. Hemagglutinin is the membrane glycoprotein of avian influenza virus responsible for receptor binding to human cells and t...

The membrane fusion reaction promoted by the paramyxovirus simian virus 5 (SV5) and human parainfluenza virus type 3 (HPIV-3) fusion (F) proteins and hemagglutinin-neuraminidase (HN) proteins was characterized when the surface densities of F and HN were varied. Using a quantitative content mixing assay, it was found that the extent of SV5 F-mediated fusion was dependent on the surface density o...

Virions from Newcastle disease virus mutants in four temperature-sensitive RNA+ groups were grown in embryonated hen eggs at the permissive temperature, purified, and then analyzed for biological properties at both the permissive and nonpermissive temperatures. At the permissive temperature, virions of mutants in groups B, C, and BC (11 mutants) were all lower in specific (per milligram of prot...